Nerve Stimulation Therapy Shows Promise In Managing Chronic
In patients with medically intractable chronic cluster headache, both 100% occipital nerve stimulation intensity(ONS) and 30% ONS intensity substantially reduced attack frequency and were safe and well-tolerated, according to recently published research reports in The Lancet.

Previously, occipital nerve stimulation (ONS) has shown promising results in small uncontrolled trials in patients with medically intractable chronic cluster headache (MICCH). Researchers aimed to establish whether ONS could serve as an effective treatment for patients with MICCH.

The ONS in MICCH (ICON) study is an investigator-initiated, international, multicentre, randomised, double-blind, phase 3, electrical dose-controlled clinical trial. The study took place at four hospitals in the Netherlands, one hospital in Belgium, one in Germany, and one in Hungary. After 12 weeks' baseline observation, patients with MICCH, at least four attacks per week, and history of being non-responsive to at least three standard preventive drugs, were randomly allocated to 24 weeks of occipital nerve stimulation at either 100% or 30% of the individually determined range between paraesthesia threshold and near-discomfort.

Because ONS causes paraesthesia, preventing masked comparison versus placebo, we compared highintensity versus low-intensity ONS, which are hypothesised to cause similar paraesthesia, but with different efficacy. In weeks 25–48, participants received individually optimised open-label ONS.

The primary outcome was the weekly mean attack frequency in weeks 21–24 compared with baseline across all patients and, if a decrease was shown, to show a group-wise difference. Findings highlighted some new facts.

• Patients were enrolled between Oct 12, 2010, and Dec 3, 2017. 150 patients were enrolled and randomly assigned 131 (87%) to treatment; 65 (50%) patients to 100% ONS and 66 (50%) to 30% ONS.

• One of the 66 patients assigned to 30% ONS was not implanted and was therefore excluded from the intention-to-treat analysis.

• Because the weekly mean attack frequencies at baseline were skewed we used log transformation to analyse the data and medians to present the results.

• Median weekly mean attack frequencies in the total population decreased from baseline to 7·38 in weeks 21–24, a median change of –5·21 attacks per week.

• In the 100% ONS stimulation group, mean attack frequency decreased from 17·58 at baseline to 9·50 at 21–24 weeks, and for the 30% ONS stimulation group, mean attack frequency decreased from 15·00 to 6·75.

• The difference in median weekly mean attack frequency between groups at the end of the masked phase in weeks 21–24 was –2·42.

• In the masked study phase, 129 adverse events occurred with 100% ONS and 95 occurred with 30% ONS. None of the adverse events was unexpected but 17 with 100% ONS and eight with 30% ONS were labelled as serious, given they required brief hospital admission for minor hardware-related issues.

• The most common adverse events were local pain, impaired wound healing, neck stiffness, and hardware damage.

"Future research should focus on optimising stimulation protocols and disentangling the underlying mechanism of action." the team concluded.

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